In an ink jet printer, a record sheet is typically fed to a sheet stacker immediately after the ink is applied to the record sheet. To reduce smudging during stacking and subsequent handling, very fast-drying inks are used. These inks have the disadvantage in that there is a tendency for the ink to dry and clog the nozzles if not used for a period of time. To solve this problem it has been conventional to provide a cap, that is, a cup-shaped cover which cooperates with the printhead when it is not in use to form an air seal around the nozzles, thereby slowing the drying of ink in the nozzles.
There is also a tendency during printing for ink to mix with dust and paper fibers and dry on the printhead surface surrounding the nozzles thus interfering with ejection of ink from the nozzles. The prior art alleviates this problem by providing a wiper which extends into the path of travel of the printhead and wipes ink from the printhead surface surrounding the nozzles as the printhead is moved back and forth relative to the wiper.
The prior art teaches that the wiper and cap may be disposed in a maintenance or service station located to one side of the record feed path. The reason for choosing this location is that in some cases the wiper and/or cap are fixedly mounted at a height such that they extend through the plane of the feed path. In other cases mechanisms are provided for moving the wiper or cap into operative positions and, as described for example in U.S. Pat. Nos. 5,115,250, 5,103,244 and 5,027,134, these mechanisms include elements which themselves extend through the plane of the record feed path.
The cap is normally made of a resilient material so that it will conform to the printhead surface around the nozzles and form an air seal therewith. The cap is also made resilient to reduce wear and possible damage to the printhead. To reduce wear of the resilient cap, the patents mentioned above propose mounting the cap on a sled which is pushed up a ramp as the printhead is moved into the capping position. The ramp provides a vertical component of movement of the cap toward the printhead but at the same time it also provides a horizontal component of movement which, if not synchronized with movement of the printhead into capping position, will still result in cap wear because of a wiping action between the cap and the printhead.